DESCRIPTION: (Applicant's Description) Greater consumption of phytoestrogens (i.e., weak estrogens of plant derivation) has been hypothesized to reduce breast cancer risk through the antiestrogenic effects of these compounds. However, the epidemiologic data addressing this relationship is limited with most studies concentrating on soy-based products. We recently began a population-based case-control study examining the relationship between non-soy sources of phytoestrogens and breast cancer risk in white, African American, and Latina women. To develop the dietary assessment instrument for this study we are collecting information on the varieties, sources, and preparation practices of beans and other potentially important sources of phytoestrogens through semistructured interviews with 140 women. However, to make the greatest contribution to understanding this etiologic relationship, more extensive data on the phytoestrogen content of foods is necessary. Thus, we propose here to utilize the data from our semistructuted interviews to identify foods and dishes to be tested for the content of seven specific phytoestrogens using state-of-the-art mass spectrometry techniques. These phytoestrogen levels will be incorporated into the nutrient database being used in the ongoing case-control study allowing us to address this important etiologic question with greater specificity, i.e., by directly examining the effects of the individual phytoestrogens and assessing these effects in conjunction with other components of phytoestrogen-rich foods, such as fiber and antioxidant vitamins.